Hydraulic apparatus



Nov. 25, 1952 c, ADAMS 2,618,933

HYDRAULIC APPARATUS Original Filed Feb. 24, 1947 4 Sheets-Sheet l JNVEN TOR. BY CECIL E. ADAMS C. E. ADAMS HYDRAULIC APPARATUS Nov. 25, 1952 4 Sheets-Sheet 2 Original Filed Feb. 24, 1947 INVENTOR- G'EC/L E. ADAMS BY 1952 c. E. ADAMS HYDRAULIC APPARATUS 4 Sheets-Sheet 3 Original Filed Feb. 24. 1947 INVENTOR. CECIL E. ADAMS BY MIKW Nov. 25, 1952 c. E. ADAMS HYDRAULIC APPARATUS Original Filed Feb. 24, 1947 4 Sheets-Sheet 4 mm m v INVENTOR. 650/]. E. ADAMS Patented Nov. 25, 1952 UNITED STATES PATENT OFFICE Denison Engineering Company,

Columbus,

Ohio, a corporation of Ohio Original application February 24, 1947, Serial No.

730,504. Divided and this application December 15, 1948, Serial No. 65,461

9 Claims.

This invention relates generally to hydraulic apparatus and is more specifically directed to a hydraulically actuated, stock-feeding attachment for hydraulic presses.

This application is a true division of my copending application, Serial No. 730,504 for Hydraulic Apparatus filed February 24, 1947.

One of the objects of this invention is to provide a feeding mechanism which will feed stock to a press or other device for performing an operation on the stock, which feeding mechanism will operate in timed sequence with the press and will uniformly accelerate and decelerate the stock in its movement thereby avoiding slippage between the feeding means and the stock with consequent greater accuracy in the feeding operation.

Another object of the invention is to provide a feeding mechanism having a fluid motor and control valve mechanism therefor which will be operative to cause the fluid motor to perform separate feeding cycles of not more than one revolution in duration spaced by inactive or rest periods in which the device served by the feeding mechanism performs an operation on the stock fed thereto.

A further object of the invention is to provide a feeding mechanism having a feed roll, a fluid motor and motion transmitting means therebetween which will provide for equal successive increments of rotation of the feed roll, the motion-transmitting means being adjustable to permit variation in the length of the increments of rotation whereby more or less stock will be fed depending upon the operations being performed.

A still further object of the invention is to provide a feeding mechanism having a feed roll, :a fluid motor and motion-transmitting means therebetween, the latter means including a oneway clutch between the feed roll and driver therefor, a crank on the driver, an eccentric operated by the fluid motor, and a connecting rod when the crank moves in the opposite direction.

Another object is to provide a combined hydraulic press and feeding mechanism having control mechanism which causes the automatic reciprocation of the ram of the press and the automatic intermittent operation of the feeding,

mechanism, the operations of the devices being alternately performed to avoid interference.

An object also is to provide a hydraulic system for the combined press and feeding mechanism mentioned in the preceding paragraph, the system having a source of fluid pressure, a reversing valve responsive to fluid pressure for initiating the operation of the press, another valve device actuated by the press to direct fluid from the pressure source to the feeding mechanism and a third valve device operated by the driving motor of the feeding mechanism for applying fluid pressure to said reversing valve to start the operation of the press when a feeding operation has been concluded.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown.

In the drawings:

Fig. 1, is a perspective View of a feeding mechanism formed in accordance with the present invention showing the same attached to a press.

Fig. 2 is an end elevational view of the feeding mechanism shown in Fig. 1.

Figs. 3 and 4 are vertical sectional views taken through the feeding apparatus showing different features of construction.

Fig. 5 is a horizontal longitudinal sectional view taken through the feeding mechanism on the plane indicated by the line V-V of Fig. 4.

Fig. 6 is a diagrammatic view of the hydraulic system employed in the press and the feeding mechanism therefor.

Referring more particularly to the drawings numeral 29 designates generally the feeding mechanism forming the subject matter of the present invention. This feeding mechanism may be used as an accessory on presses of various types, but for purposes of illustration, it is shown in the drawings as an accessory for a hydraulic press, this device being indicated generally by the numeral 2i. The press 2| includes a frame 22 having a bolster section 23, an upright column 2%, and a head section 25, the head and bolster sections projecting forwardly from the column 24. The head section has a power cylinder 26 supported therein, this cylinder receiving a piston 2? from which a ram 23 projects toward the bolster section 23. When movement is transmitted to the piston 27 to cause reciprocation thereof in the cylinder 26, the ram 23 will be moved toward and away from the bolster section.

The head section also receives a control valve 35 which may be of any suitable type, the one illustrated being of the type shown in co-pending application, Serial No. 600,736, filed June 21, 1945, now Patent No. 2,561,766, issued July 24, 1951. This valve, shown diagrammatically in Fig. 6, operates to control the flow of fluid from a pressure source 3| to the power cylinder to secure the automatic operation of the piston and ram. The pressure source 31 includes a reservoirtz, a motor driven pump 33 and a relief valve 35, the latter being adjustable to vary the pressure in the hydraulic system at which the discharge from the pump 33 will be bypassed back to the reservoir 32. A fluid line 35 extends from the pressure source to the control valve 30, this fluid line being in open communication with the inlet port 35 of the valve 38. While this valve has been described in detail in the patent above referred to, it will also be described herein sufiiciently to facilitate the understanding of the present invention.

Valve includes a body casing 31, which is formed with a pair of vertically extending bores 38 and 48. Body 37 is also formed with a plurality of annular grooves M to 41, which are spaced longitudinally of, and open into, the bore 38. The body is further formed with annular grooves 43, 49, and 55, which are spaced longitudinally of, and open into, the bore 40. Bore 38 receives for sliding movement a spool 52 having an internal chamber 53 and a plurality of longitudinally spaced sets of ports 54 to 60, inclusive, formed in the side wall thereof. Certain of these ports register with certain of the grooves 4! to 41 in various positions of movement of the spool 52 in the bore 38. The upper end of the chamber 53 is closed by a cap 82 in which a recess 63 is formed, this recess opening to the under side of the cap. The upper end of the coil spring 64 is received in the recess 63, the lower end of this spring being disposed in a socket 85 formed in a shuttle valve 66 disposed for sliding movement in the chamber 53 of spool '52. The shuttle valve 66 comprises a cylindrical member having an external groove 81 formed in the wall thereof, intermediate the ends of the cylinder, this groove providing spaced heads 58 and 78 on the spool. The shuttle valve is also provided at the head portion '88 with transversely extending ports H which communicate at their inner ends with a chamber 12-. Axial ports 13 and 14 are formed in the shuttle valve, the former extending from the chamber 72 to the socket 85 and the latter extending from the chamber 12 to the lower end of the shuttle valve. The coil spring 64 normally retains the shuttle valve in its lowered position with the lower end thereof in engagement with the bottom wall of the chamber 53 in spool 52.

The spool 52 has a rod 75 projecting from its lower end through a cap 18 secured to the bottom of the body 31. This rod is connected at its lower end to another rod H commonly termed the shipper rod, this rod receiving a collar 18 which is adjustably secured to the rod and is engaged at certain stages of operation of the ram 28 by the end of an arm 88 secured for movement with the ram. When the ram moves in an upward direction and approaches the upper limit of its travel, the arm 80 will engage the collar 18 and move the rod 11 in an upward direction. This movement is transmitted by rod 15 to the valve 52 causing the latter to move to a position wherein fluid flow to the lower end of the power cylinder to effect upward movement of the ram will be interrupted. When this event occurs, the ram will come to rest in a raised, inoperative position ready for another cycle of operation. Ports 5B in spool 52 communicate at all times with groove 35, which is in open communication with the inlet port 38, thus fluid from the pressure source may flow through the ports 58 into the chamber 53 at the groove 6! formed in the shuttle valve. When the par-ts of the valve are in the position shown in Fig. 6, which position will be assumed when the ram 28 is at rest, fluid admitted to groove 61 may flow outwardly from the chamber 53 through ports 51 into groove 44.

Body 3"! has a drilled opening Bl formed in one side thereof, which opening communicates at its inner end with the groove 44 so that fluid admitted thereto may flow from the groove to bore 45 and from the latter through the outer portion of opening 8| to a line 82. The fluid admitted to the bore 40 when the parts are in the positions shown in Fig. 6 is prevented from flowing longitudin-ally thereof by a spool 83 disposed for movement in the bore '48. This spool has longitudinally spaced heads 84 and 85 which engage the ide walls of the bore 40 and control communication between the portion of the bore 48 between heads 84 and 85 and the groove 49, head 84 serving at all times to prevent communication between that portion of the bore and the groove 48.

Normally, the spool 83 is yieldably retained in a centered position by coil springs 86 and 8! disposed at the ends of the spool between the end caps for the body 31 and shoulders formed on the spool and a spring abutment 88. When in the centered position, under the influence of the springs, the space around the spool 83 between the heads 84 and 85 will be in communication with groove 46 surrounding bore 38. Groove 46 is connected, when the parts of the valve mechanism are in position to maintain the mechanism inoperative, with the reservoir 32 through ports 59 in spool 52, chamber 53, ports 68, grooves '41 and 50 and exhaust line 98, thus fluid under pump pressure will be bypassed directly to the reservoir 32 when the mechanism is idle, without imposing a burden on the pump-operating motor. Spool 83 is adjusted in bore '40 by an eccentric pin 9! supported for oscillation in the lower portion of the body 31, a shaft 92 projecting from the support for the eccentric pin to the exterior of the mechanism to effect the manipulation of the pin. By such rotation of the support, the spool 83 may be lowered from its centered position, wherein pump flow is discharged to reservoir 32 to the position shown in Fig. 6 which provides for automatic operation of the press and the feeding mechanism 28.

When the spool 83 is in the latter position and spool 52 also is in the position shown, pump fluid will be directed through the line 82 to a second control valve mechanism 93 which is attached to the rear end of a fluid motor 94 employed to drive the feeding mechanism. Fluid motor 94 may be of any suitable type, the one illustrated having an .inlet port 95 and an outlet port 96. Valve 93 has a passage 81 which establishes direct communication between the line 82 and the motor inlet 95, thus, fluid supplied to line 82 will flow directly into the fluid motor to efiect the operation thereof. This fluid will be exhausted through the outlet port 98 into a passage 98 formed in valve 93. Passage 98 leads to the out let port I80 of the valve mechanism, 93, which outlet port is connected by a line I 0| with reservoir 32. As long as fluid is permitted to flow to the fluid motor 94 and outwardly through the outlet passage 98, port I and line IBI to the reservoir, the fluid motor will operate. The rate of operation may be controlled through the adjustment of a bypass valve I02 which is disposed in a passage I03 extending between the passages 91 and 98 in the valve 93. When the fluid motor 94 operates, due to the flow of fluid therethrough, the operating shaft IEM thereof will be rotated. This shaft projects from the fluid motor 94 and is keyed at its outer end to a hub I05 journalled in bearings I06. The hub has an eccentric portion ID! the purposes of which will appear as the description proceeds.

The outer portion of the hub m5 is provided with an enlargement we in which a dove-tail groove is is formed. This groove slidably receives a member II!) from which a crank pin IlI projects. The ends of the groove H39 are closed by plates H2 which support for rotation an adjusting screw IIZ-A, this screw being threaded through the member I I5} and serving, when rotated, to vary the longitudinal position of the member I I0 in the slot. In this manner, the distance between the axis of rotation of the hub I 95 and the crank pin may be varied. Crank pin I I I pivotally receives one end of a connecting rod I I3, the opposite end of which is similarly connected to a pin I Hi on a crank arm I I5; this crank arm is secured to a shaft I It which is in turn keyed to the driver section I I! of a one-way clutch.

This clutch includes a driven section I I8 which is formed with or suitably secured to a feed roll I23, the latter being journalled for rotation in a frame 12 l. Motion is transmitted from the driver section I I! to the driven section Ila through the provision of spring-pressed balls I 22 disposed between angular surfaces I23, formed on the driver, and the inner surface of the driven section IIB. When the driver section is revolved in the direction of the arrow in Fig. 3 the balls I22 will be wedged between the inclined surfaces I23 and the driven section locking the sections together for rotation in unison. Movement of the crank arm IE5 to cause rotation of the section H1 in this direction is caused by rotation of the driving motor and the motion of the crank end 589 operated thereby. This movement takes place during one-half a revolution of the motor shaft. During the other half of such a revolution, the driver section 5 l! is revolved in the opposite direction. Such movement will not be transmitted to the driven section and feed roll since the one-way clutch permits relative movement between these elements when the motion of the driving section reversed.

The feed roll is positively prevented from backing up or overrunning by a brake IN comprising a lined band I25 which is connected at one end to the frame as at I25 and at the opposite end to a, spring-pressed block I2l, this block being engaged by a rod I25; which is secured to a split collar l3!) surrounding the eccentric portion Ill! of the hub 35. The eccentric Nil is so related to the crank pin I l I that the brake will be applied at the prop-er time to prevent overrun or reverse movement of the feed roll. The degree of rotation of the feed roll during each forward movement of the driver member is regulated by the adjustment of the member Iii} relative to the axis of rotation of the hub IE5.

In order that the stock being fed by the feeding mechanism will be frictionally held in contact with the feed roll, there is provided a pressing roll I3I which is journalled in suitable bearings I32 carried by the frame I2I. The presser roll I3I is resiliently urged toward the feed roll by coil springs I33 disposed between the upper sections of the bearings I32 and adjusting screws I34. Through the adjustment of the screws I34, the force of the springs I33 may be varied to cause more or less friction between the stock and the feed roll. A pair of guide rollers I35 are mounted for rotation about vertical axes on a transversely extending web of the frame at the inlet side of the feed roll, to center the stock between the feed rolls, these guide rollers also tending to eliminate friction which might affect the feeding operation.

In the operation of the press and feeding mechanism, the press ram and feeding rolls are alternately operated, the latter performing a feeding operation for each revolution of the driving motor 94. To effect the alternate operation of the ram and feed roll, the valve 93 is provided with a poppet I3! disposed in the passage as. This poppet is normally maintained in an open position by a spring I38 in order that the fluid discharged from the fluid motor may flow to exhaust without appreciable obstruction. After the feed roll has advanced the stock toward the ram and the driving motor 94 executes a portion of the second half of the revolution, the poppet I3! is actuated to interrupt the flow of fluid to exhaust and direct the same through a second outlet or control port Mil. To close poppet I37, the motor shaft Hit is provided with a cam ItI which engages a roller I42 provided on the end of a plunger M3, this member being disposed for sliding movement in the frame work of the feeding mechanism. The outer end of the plunger I 43 engages one arm I44 of a bell crank I45 the second arm MB of which engages one end of a push rod I41; this push rod in turn, engages the outer end of a stem formed with poppet I3! and projecting from the casing of the valve 93. A suitable compensating connection I 48 forms a part of the push rod IM to absorb additional movement, after the poppet is closed, and prevent injury to th mechanism. After the poppet valve has been closed, fluid discharged from the fluid motor at will flow through line I56 to groove 48 in valve body 3?. This groove communicates with groove l2 which in turn communicates through ports 55, with chamber 53 at the lower end of the shuttle valve 66. Fluid thus introduced into the lower end of the chamber 53 Will move the shuttle valve upwardly in opposition to the force of the spring 64 until groove 6'! in the shuttle valve establishes communication between the inlet line 35 and the groove it through groove 45 and ports 58 and 5%.

After shuttle valve 65 has been elevated the flow of exhaust fluid from motor 24 will be obstructed with the effect of stalling the motor. Before this motor stalls, however, the volume of fluid necessary to elevate the shuttle valve exhausted by the motor is sufficient to permit motor G l to advance far enough to cause the high point on cam IQI to pass follower I42. This action would normally permit poppet E31 to return to an open position but due to the pressure existing beneath the shuttle valve, in line lEfl and passage 93 the poppet is retained in closed position.

Since groove 46 is connected by line I5I with the upper end of power cylinder 26, the placing of the shuttle valve in an elevated position will connect the source of fluid pressure with the upper end of the power cylinder. At this time also, the lower end of the power cylinder will be in communication with the reservoir 32. This communication takes place through line I52,

7 groove '43, ports 55, or 55 in the spool 52, ports 'II-in the shuttle valve, chamber I2, passage I3, socket 65, ports 69, grooves 41 and 50, and line 90. Flow of fluid along this path will be restricted due to the reduced size of the passage 13 causing a back pressure to build up in the chamber I2, the lower end of the power cylinder and the passages connecting these members. This back pressure is transmitted to the lower end of the chamber 53 through passage I4 and serves to maintain the pressure previously introduced through line I50. The shuttle valve 65 will thus be retained in an elevated position and poppet I31 will be held closed during the downward movement of the ram. When movement in this direction is initiated, the arm 80 will move away from the collar I8 permitting the shipper rod and valve spool 52 to move downwardly in response to the force of a spring I53 disposed in the valve casing 31 between a washer I54 and a collar I55 surrounding rod 15, until ports 51 move out of registration with groove 44, at this time the path of fluid flow to the fluid motor 94 will be obstructed. Full pump volume will then be available for the operation of the ram and fluid motor 94 will remain idle until arm 80 again engages collar I8 during the return movement of the ram, and moves valve spool 52 to reestablish communication between ports and groove 44. When this communication is reestablished, the feeding mechanism will again be operated and the ram will remain stationary until another charge of fluid under pressure is supplied to the underside of the shuttle valve to initiate another operation of the ram.

Return or upward movement of the ram occurs after the ram has exerted the force determined by the setting of relief valve 34. When this valve operates to spill fluid directly from the pump 33 to reservoir 32 the ram ceases to move in a downward direction and the exhaust flow from the lower end of the power cylinder ceases. The back pressure is then dissipated through passages I3 and I4 and shuttle valve 66 is moved to its lowermost position by the force of spring 64. When the back pressure is dissipated, spring I38 moves valve I31 to an open position also and the mechanism is in condition for another cycle of operation which will occur as soon as the ram reaches a fully retracted position if the spool 83 is properly positioned as previously mentioned.

From Fig. 6 it will be noted that line I59 contains a restriction I55. This restriction serves to insure the retention of poppet I31 in closed position immediately after it has been closed by the push rod I 4'! even though the push rod is retracted due to the high point on cam I lI passing follower I42. Inasmuch as a poppet valve is used which poppet will readily open because of the relatively slight displacement of fluid, the use of the restriction in line I50 is desirable. This restriction is located in close relationship to port I40 and although it serves to obstruct fluid flow to retain poppet valve closed, such obstruction is insuflicient to deleteriously affect the opening of the poppet valve when the ram stops moving downwardly and the shuttle valve drops.

The cam MI is provided with a relatively sharp projection to reduce the tendency of the device to stop with the poppet valve closed.

From the foregoing it will be apparent that a feeding mechanism has been provided which will operate to successively feed stock to a ram or other device for performing operations thereon.

It will also be apparent that a hydraulic system has been provided. for both. the press and the feeding mechanism, which, system provides for the alternate operation of the press ram and the feeding mechanism, each of these elements being retained in inactive condition during the active condition of the other. Due to this alternate operating arrangement no interference of one .mechanism with the other can result.

I claim: a a

1. A hydraulic system comprising a source of fluid pressure; a power cylinder having a ram; a fluid motor; valvemeans between said fluid pressure source and said power cylinder, said valve means being operative to direct fluid to said power cylinder to cause a single cycle of operation thereof and to then direct fluid to said fluid motor; and a second, valve means operative to direct fluid discharged from, said fluid motor to exhaust during a portion of a cycle of operation thereof and to thereafter direct such exhaust to said first valve means during another portion of the cycle of operation of said motor to initiate the operation of said power cylinder.

2. A hydraulic system comprising a source of fluid pressure; a power cylinder having a ram; a fluid motor; valve means between said fluid pressure source and. said power cylinder, said valve means being operative to direct fluid to said power cylinder to cause the advance and retraction of the ram thereof and to'then direct fluid to said fluid motor; a second valve means operative to direct fluid discharged from said fluid motor to exhaust during a portion of a cycle of operation thereof; and means operated by said fluid motor during another portion of the cycle of operation thereof to actuate said second valve means to thereafter direct fluid discharged from said fluid motor to said flrst valve means to dispose the same in position to interrupt the flow of fluid to said motor and initiate the operation of said power cylinder.

3. A hydraulic system comprising a source of fluid pressure; a power cylinder having a ram; a fluid motor; valv means between said fluid pressure source and said power cylinder, said valve means being operative to direct fluid from said source to said power cylinder to cause a cycle of operation thereof and having an element operated by said ram adjacent the termination of said cycle of operation to direct fluid from said pressure source to said fluid motor; and a second valve means operative to direct fluid discharged from said fluid motor to exhaust during a portion of a cycle of operation thereof, said second valve being actuated by said fluid motor adjacent the termination of a cycle of operation thereof to direct fluid discharged from said motor to said first-mentioned valve means to interrupt fluid flow to said fluid motor and initiate a cycle of operation of. said power cylinder.

4. A hydraulic system comprising a source of fluid pressure; a power cylinder having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means being operative to direct fluid from said source to said power cylinder to cause a cycle of operation thereof consisting of the advance and retraction of said ram and then direct fluid from said pressure source to said fluid motor; a second valve means normally operative to direct the discharge from said fluid motor to exhaust; means actuated by said fluid motor at one stage in each revolution thereof to shift said second valve means to momentarily direct fluid discharged from said fluid motor to the first-mentioned valve means to terminate fluid flow to said fluid motor and initiate an operation of said power cylinder; and means operated by said ram adjacent the termination of each cycle of operation of said power cylinder to interrupt the flow of fluid to said power cylinder and resume the flow to said fluid motor.

5. A hydraulic system comprising a source of fluid pressure; a power unit having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means having an element responsive to fluid pressure to initiate the operation of said power unit; flow directing means in said valve means actuated by said ram adjacent the termination of a cycle of operation to connect said fluid motor with said fluid pressure source; a second valve means normally operative to direct the discharge from said fluid motor to exhaust; and means for transmitting movement from said fluid motor adjacent the end of a cycle of operation thereof to said second valve means to interrupt the flow of discharge fluid to exhaust and apply the same to the fluid pressure responsive element of the firstmentioned valve means to initiate a cycle of operation of said power unit.

6. A hydraulic system comprising a source of fluid pressure; a power unit having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means having an element responsive to fluid pressure to initiate the operation of said power unit; flow directing means in said valve means actuated by said ram adjacent the termination of a cycle of operation to connect said fluid motor with said fluid pressure source; a second valve means normally operative to direct the discharge from said fluid motor to exhaust; and cam means actuated once during each revolution of said fluid motor to close said second valve means and interrupt the flow of discharge fluid to exhaust and apply the same to the fluid pressure responsive element of the first-mentioned valve means to initiate a cycle of operation of said power unit.

7. A hydraulic system comprising a source of fluid pressure; a power unit having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means having an element responsive to fluid pressure to initiate the operation of said power unit; flow directing means in said valve means actuated by said ram adjacent the termination of a cycle of operation to connect said fluid motor with said fluid pressure source; a second normally open valve means in the outlet of said fluid motor; a branch line extending from said fluid motor outlet in advance of said second valve means to the pressure responsive element of said first-mentioned valve; and means operated once during each revolution of said fluid motor to close said second valve means to interrupt the discharge of fluid from said fluid motor to exhaust 10 and direct the same through the branch line to said fluid pressure responsive element of the firstmentioned valve means to initiate a cycle of operation of said power unit.

8. A hydraulic system comprising a source of fluid pressure; a power unit having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means having an element responsive to fluid pressure to initiate the operation of said power unit; flow directing means in said valve means actuated by said ram adjacent the termination of a cycle of operation to connect said'fluid motor with said fluid pressure source; a second normally open valve means in the outlet of said fluid motor; a branch line extending from said fluid motor outlet in advance of said second valve means to the pressure responsive element of said first-mentioned valve; a flow resisting element in said branch line and means operated once during each cycle of operation of said fluid motor to close said second valve means to interrupt the discharge of fluid from said fluid motor to exhaust and direct the same through the branch line to said fluid pressure-responsive element of the first-mentioned valve means to initiate a cycle of operation of said power unit.

9. A hydraulic system comprising a source of fluid pressure; a power unit having a ram; a fluid motor; valve means between said fluid pressure source and said power cylinder, said valve means having an element responsive to fluid pressure to initiate the operation of said power unit; flow directing means in said valve means actuated by said ram adjacent the termination of a cycle of operation to connect said fluid motor with said fluid pressure source; a second valve means normally operative to direct the discharge from said fluid motor to exhaust; a by-pass valve in said second valve means, said by-pass valve being adjustable to vary the quantity of fluid admitted to said fluid motor to control the rate of operation thereof; and means for transmitting movement from said fluid motor adjacent the end of a cycle of operation thereof to said second valve means to interrupt the flow of discharge fluid to exhaust and apply the same to the fluid pressure responsive element of the first-mentioned valve means to initiate a cycle of operation of said power unit.

CECIL E. ADAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,695,327 Gcldston Dec. 18, 1928 1,799,113 Miedbrodt Mar. 31, 1931 2,016,710 Ferris Oct. 8, 1935 2,054,296 Merrill Sept. 15, 1936 2,182,908 Wegerdt Dec. 12, 1939 

